I have a qustion someone might be able to help me with. A farmer asked me today if he could install 60 347 volt lights. He does not have a neutral on his primary service going into his building. Can this be accomplished without the use of transformer to provide a neutral to install these lights.....

Thanks

Clyde: When you mention service neutral, are you talking about a service or are you talking about a feeder. A service has to have a neutral, see 4-022 (3). If it is a 600V feeder, 347V can (in theory) be obtained by a wye connection, but this is not acceptable to code. The star point is a neutral and has to be grounded at the service, 10-106 (1),(b) and 10-204 (1),(a).

why not just go 600v lighting?

The problem is this farmer is pretty cheap. He was given the 347 volt light fixtures and is not really interested in spending any money.
The service is quite old and is only a three wire, 600 volt. 400 amp.
I did a little research and the only thing I can find is that he needs a transformer at least 25kva.
Something about doing mostly control work, you don't get a whole lot of experience with this sort of thing.
Thanks for your help.

If Canadian Codes permit and the building service is ungrounded 600V 3-wire, it may be possible to assemble a zig-zag grounding autotransformer to provide a neutral for the 347V fixtures. Three drytype transformers rated 240 x 480 Volts–120/240 Volts would be OK for up to 360V ø-n. [Alternate rating 120 x 240 Volts – 120/240 Volts]

The arrangement for operating 277V lighting on a 480V ungrounded service is described in: www.ecmweb.com/ar/electric_unconventional_transformer_connections In this case, three 1½KVA transfomers permitted 18.75A/ø.

Clyde — What is the namplate current on the sixty 347V fixtures?

[If you like, I can post a typical interconnection diagram when the local server is back up.]

The name plate currant is 1.2 amps.

just curious but if you open up the cover to these fixtures they might be a multi tap ballast,or you might want to ask manufacturer if they can be changed to 6oov,easily.

 

 

Looks like 24 amperes/ø. So, that would translate to a set of 2kVA 240x480–120/240V drytypes, or 120x240—120/240V units, with appropriate connection changes in the diagram.

Note that in NFPA territory, the arrangement is permitted by 99NEC450-5, with attention paid to the overcurrent-device location in the circuit.

Maybe its worth inquiring to see if the power authority can upgrade the service to include a neutral?

(I haven't a clue what the transformer solution is worth.)

With the plans to upgarde in the next few years, a poer upgrade at this point seems to be the most logical course of action. Thats what he's planning to do now.

thanks for your help guys.

Clyde

Given a power upgrade is in the future, there is some merit in maintaining a 3phase delta system. Harmonics, efficiency ground fault protection and other topics come to mind.

For those circuits that are in need of a 347 volt source and given there are times when the load is not balanced, an artificial neutral may be a consideration. The auto transformer connections provided by Bjarney appear to provide an artificial neutral but "tuning" may be a problem. Any change in load characteristics re: size or load sharing may be an issue. As well, the capital cost of the 1.5 kva xformers may be about the same cost as 22.5 kva delta/star dry core 1/1 ratio transformer.

I should ask what the rural voltage in Clyde's area is. Is there 600 volt 3P4W primary easily available or will the upgrade have to deal with a 3P3W in any event? Wiull the local utility provide a 4 wire system but at what cost?

I know in a lot of Rural Ontario 3P3W @600 volt is a local utility voltage -- 4160 on up to 35KV and a transformer allowance as part of bigger projects.


Just thinking out loud.....

Doug.....et al

I must disagree with the need for “tuning”. For all practical purposes, the ZZA set should be able to efficiently operate 20 fixtures [24 amperes at 347V] on one phase-to-derived-neutral connection. That is one of the accepted capabilities of grounding transformers for serving potentially unbalanced loads.

I hear ya!!1

I guess I was looking at a standard off-the-shelf method of an economical code
approved device with some extra capacity. Some of the inherent problems of ground fault etc are important factors as well.

There are so many options one has to be selective to ones immediate process.

Although FPE is not a very good example because of some bad history in the US but the following URLS are interesting to review.

This URL is the Canadian arm of Schneider. They have a good write up on the subject as well.
http://www.schneider-electric.ca/www/en/products/ground/html/general.htm

Section 4 of the PDF file at the following URL is interesting from Powercon Corp of Maryland.
http://www.powerconcorp.com/docs/pcib-1031.pdf

Doug......et al